1. Field of the Invention
The present invention relates to a variable valve apparatus, in an internal combustion engine including valves, which controls opening and closing of the valves, and an engine apparatus and a transport machine including the same, and more particularly to a technique for switching a lift amount of the valves between a time of low speed and a time of high speed.
2. Description of the Related Art
Conventionally, as this type of apparatus, there is a variable valve apparatus including a cam shaft having a cam for low speed and a cam for high speed, a rocker shaft interposed between the cam shaft and a valve, and having a rocker arm for low speed and a rocker arm for high speed, pinholes provided in the rocker arm for low speed and the rocker arm for high speed, and formed in positions close to the rocker shaft as seen from the axial direction of the rocker shaft, a switching pin slidably mounted in the pinholes, and a hydraulic piston for driving this switching pin (see Unexamined Patent Publication H11-141322 (FIGS. 2-5), for example).
This apparatus, with the switching pin withdrawn by the spring force of a coil spring, causes the rocker arm for high speed to rock idly, and causes only the rocker arm for low speed to act on a stem end surface of the valve. With the switching pin advanced by the hydraulic piston, the rocker arm for high speed and the rocker arm for low speed are interlocked for causing the rocker arm for low speed to act on the stem end surface of the valve with operation timing of the rocker arm for high speed. This can switch the rocker arm for low speed and the rocker arm for high speed for acting on the valve.
However, with the above construction, the forward end of the switching pin can collide with an opening edge of a pinhole, thereby failing to perform a connecting operation normally. A taper-like chamfer is formed on the opening edge of the pinhole so that the switching pin may advance to the pinhole easily (see U.S. Pat. No. 2,617,343 (FIG. 5), for example).
However, the conventional example with such construction has the following problem.
That is, the conventional apparatus, with the taper-like chamfer of the pinhole, facilitates advancement of the forward end of the switching pin. However, when the switching pin is advanced, the rocker arm for high speed can be pushed by the cam for high speed to flip the forward end of the switching pin at the time when the forward end of the switching pin contacts the tapered surface. Therefore, there is a problem of easily producing a situation where the rocker arm for low speed and the rocker arm for high speed cannot be connected. With such a low certainty of connection, it becomes impossible to acquire a desired operating state.